edit Since people seem to have the wrong impression, I never planned on walking in dressed like a slob. A button down shirt, tucked into nicer pants with nicer shoes on. Maybe a tie if I could find one that looked nice. I just never planned on wearing a full matching suit.
Let the downvotes rain you jacket-less tie wearers.
On topic: OP, you're never going to be dinged for wearing a suit to an interview. You may be taking a chance by dressing down. How people perceive you at first glance does matter, whether we like it or not.
Personally, I would wear the suit. That said, I have been involved in more than a few interviews/hiring decisions, and I've never rested my decision on dress (if you showed up in shorts and a T-shirt there may be an issue as it says something about your attitude.) I wouldn't give a leg up to the candidate who wore a suit over the candidate who wore a button up and chinos, but that's me, and we all know that dress isn't exactly something which is on the mind of many engineers.
I'd say "you wouldn't want to work for anyplace that would ding you for a suit". At least I wouldn't.
But now that we have CEOs wearing everything from suits to sweatshirts, there's no way you could possibly be expected to magically know what a company's dress code is ahead of time. :)
The other seems more formal. 70 people, teaching software. The phone screen was with an HR person who was dressed nicely, although she brought up beer a number of times (which was awesome).
I guess my biggest fear is "over" dressing? As in, I'm presumed to not be a cultural fit because I overdress. Gameplan was to dress nicely, but not in a full suit. I might even wear a tie, but a full suit to me seems excessive.
If the role is purely for programming, and your impression is that the other developers at this company do not wear them, I would not wear a tie and jacket- it could come off as an incorrect cultural fit.
I don't think you'll feel overdressed in any work environment if you wear a button up shirt, comfortable slacks, and understated dress shoes.
The dress code for someone applying to some kind of professional job is (in the Western world - not everywhere in the world wears English national dress when they want to look smart) a suit, smart shoes, nice tie (or a female equivalent). Doesn't necessarily have to be the same material for trousers and jacket, but smart trousers and a good condition jacket. That is the dress code for a job applicant.
The dress code for the workplace at which you are interviewing might be different, but you don't work there so that's not your dress code; you're a job applicant at an interview. Someone dressing smartly has gone to the effort of dressing well, and in doing so has indicated that they have prepared for this interview, and that they recognise the formality of it; they are demonstrating basic good manners, and good manners should be a cultural fit in every workplace.
Sadly, I suspect there are workplaces who want you to be psychic and guess how to dress to match them exactly so they think you're "one of them" and mark people down for dressing smartly and not looking just like them, even though you don't even work there. I'd like to say that such workplaces are not worth your time, but sadly it wouldn't be true (although they may well have bought a little bit more into some kind of hipster inspired cargo-cult than you might like). Nonetheless, all you can do is play the probabilities, and on balance dressing smart for a job interview will win you more points than dressing like them.
When I interview, if they're not dressing smartly, it goes against them, even though most people around the office do not dress nearly so smartly.
Ironically, these people are often found to heavily support the idea of beautiful interfaces and advocate how important appearance is in UI and so forth; well, a conversation with a person is very much a UI for getting a job.
It's not a myth of startup companies are actually hiring developers who show up in jeans, tshirt and tennis shoes.
For mid-sized firms it can go either way, suit or just business attire with or without tie.
For small firms, dress appropriately to the company, as someone else said, dress at least 1 level up from what they are wearing daily.
Also, you can always ask the phone screen person or HR rep. Say hey, what is the daily dress code like? Or be more direct and say hey I like to make sure I am respectful of your environment and would normally wear slacks and a button down shirt, would that be acceptable for an interview with your team? Frankly I have had only a few people ever ask me and they stood out in my mind positively as conscientious.
Financial services/banks etc, always wear a suit. A few other industries are like this too from my experience.
Actually, i think this is the key. Not because it's an easy way, but because that is exactly what an interviewee's task in a job interview is:
Finding out basic facts about the company.
Sure, there are outliers -- Goldman Sachs probably won't hire you unless you show up for the interview in a tuxedo, and some brogrammer-laden startups won't hire you unless you dress exactly like they do -- but they're rare, and recruiters will warn you ahead of time if you're walking into that kind of situation.
Personally, I would rather hire a solid programmer who needed some guidance on how to dress than a solid dresser who needed guidance on how to program, but that's just me.
I'm not saying that dressing casual would improve your chances; I'm saying that you are very likely to be the only one who cares what you wear to your interview.
edit: I didn't actually say FUCK YOU to anyones face.
Wearing a suit to a hipster office certainly isn't going to loose you the job, they'll be more inclined to look at the person rather than the suit.
Wearing a suit to a corporate role will certainly help get you the job.
Wearing a suit makes you look good, looking good isn't a requirement for day to day work, but there are occasions you should smarten up. An interview is definitely one of those occasions.
Wear a full suit, feel comfortable in it and know you are looking your best and presenting the best side of you.
If the company doesn't give you guidance, I think it's easiest to ask. Usually you're dealing with a recruiter at the company and they want to get someone good hired, but ultimately the choice to hire won't be theirs. They're not going to want you to get a "no" decision simply because someone interviewing you didn't like your dress. They know the people who will be interviewing you and what they're expecting. If the company keeps track of numbers for these inside recruiters, those recruiters are going to want to look like they're bringing in good people - that they have good judgement when bringing people in for interviews. They won't want their numbers to be bad based on your dress - based on a technicality. How crummy would that be - your numbers are worse than another recruiter's because you wouldn't advise candidates on how to dress and they were denied because of that?
You can always fall back to being more dressy, but I think asking is the easiest.
I do not comment on attire during the interview, not my own, nor anyone else's. If I am asked about it, I say "This is what I wear to work. Does your company have a dress code?" Regardless of the answer, this is a warning signal, and my salary expectation just jumped. The interviewer permanently lost its potential discount for work environment.
I may even keep my existing employee ID on its neck band and tucked inside my shirt pocket, to reinforce the signal that I already have a job (and you're keeping me from it).
When I interview while unemployed, I'm far more likely to wear the suit. Or at least a tie. My hoop-jumping reserves not being depleted by an existing employer, I am far more willing to acquiesce to expectations not relevant to the job description. It's very much like the difference in dressing up for a date night versus going out with your spouse.
For a safe bet, nice pants and a nice shirt let's them know you prepared and that the company is worth your time. Dressing down too much is not helpful. On the flipside, wearing a suit is actually overkill and may lead to impressions you are hiding something (unless you are going to be in finance). Developers don't really trust the suit, especially in the game industry.
As long as you feel confident in it you will do well. You might be in interviews for many hours for each one, bring water and make sure you are comfortable.
Next choice, out of the regular work wardrobe, is to wear the clothes I am happiest wearing. These are the ones that are a bit like a wrap-around comfort blanket.
For me, most important is to actually be clean. I couch-surfed my way to one interview some years ago, where there was a problem with the water. I could not shower or even do a minimal effort wash. I felt horrible and I did not get the job.
One idea though, if you work primarily with one programming language/application/framework, then, if you have any merchandise - e.g. a hat or a T-shirt emblazoned with the language/app/framework logo - then that could work and break the ice.
For C-level positions or if you are interviewing in the finance industry, wear a suit.
